Grassham pleaded guilty before Judge Douglas McGill SC to burglary by being in a dwelling with intent, assault causing bodily harm when armed (with a golf club), assault on the woman causing bodily harm when armed, and wilful damage of a television.

"I'm sorry," she said to his Honour when he asked if she had anything to say.

Sandra Cupina for the Crown said the man had been with another young woman when Grassham entered the shed with the intent to assault him.

Ms Cupina said Grassham punched the man in his face a few times, then armed herself with a golf club and hit him with it several times.

She also swung a golf club and hit the man's arm as he tried to protect his face, then threw the club, hitting the woman.

After hitting the woman in the ribs Grassham was pulled away.

"His jaw was fractured, his right arm bruised and swollen," Ms Cupina said.

"The woman suffered marks to the side of her head and bruising."

Ms Cupina said the Crown maintained the incident was serious as the violence was protracted, had taken place in someone's home and involved the use of an implement.

Defence barrister Maree Willey said the teenager had had a difficult childhood mixing with the wrong crowd, and the result could be seen in her criminal history.

Ms Willey said Grassham was asked to go to the shed by another friend for drinks and had no intention of carrying out an assault.

"She was grossly intoxicated and says she drank two bottles of vodka that night," Ms Willey said.

"He had been in a relationship with a friend of hers and when she became pregnant he ended the relationship. She was particularly angry at him.

"It is no excuse but gives some reasoning for what she did."

Ms Willey said Grassham was now making efforts to rehabilitate herself and move forward with her life.

Judge McGill said he was not told if there had been any provocation for her behaviour.

He warned that if there were further offences the court would have no option but send Grassham to jail.

He imposed an intensive corrections order of nine months, to be strictly supervised by Corrective Services, which would also include unpaid community service work.